The solution got into the groundwater, which flows toward the Passaic River, about 2,500 feet west of the site.

The city's drinking water comes from a different source and is not contaminated.

The plume is about three quarters of a mile long and slightly more than an eighth of a mile wide, said Rich Puvogel, a project manager with the EPA.

Detecting chromium in groundwater, soil and homes does not necessarily mean that people were exposed, Zelikoff said.

"We hope to be able to relieve their anxiety," said Zelikoff, noting that scientists will begin recruiting volunteers for the toenail clippings within the next three weeks.

Toenails grow slowly and may help to detect chronic exposure, she said.

Very high levels of chromium were found at the factory - approximately 80,000 parts per billion, Puvogel said. Downstream from the site, the levels drop off by several orders of magnitude, he said. New Jersey sets a limit of 70 parts per billion.

The residents' exposure would have come from inhaling or touching chromium that had seeped into their basements, especially during flooding.

"When the water dries, it also leaves a chromium dust residue," Zelikoff said.

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Inhaled chromium is a carcinogen that increases the risk of lung cancer, according to the EPA.

Scientists, who became aware of the contamination last year, want to test up to 250 residents, including some who live directly above the plume and a control group living at least three miles away, Zelikoff said.

Residents who agree to submit toenail clippings will receive kits containing stainless-steel clippers and instructions. They must be between 18 and 65 and cannot have taken chromium supplements or be smokers.

Last year the EPA removed more than 753 containers and drums of industrial waste from the factory and 6,100 gallons of chromium-contaminated water. The building was demolished in October.

Next week the agency will start sampling the soil at the site to determine what sources of contamination remain.

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